Adapting to delay spread variation in wireless communication systems

ABSTRACT

Methods, systems, and devices for wireless communication are described. A user equipment (UE) and base station may dynamically update a reference signal pattern, a symbol prefix configuration, or both based on channel propagation conditions such as a delay spread, multipath propagation, or frequency selectivity. In some cases, the UE may measure the channel propagation conditions and send an indication to the base station. The base station may then update the reference signal pattern or symbol prefix configuration accordingly, and send an indication of the new configuration to the UE. In some cases, i.e., for uplink communications, the base station may measure the channel propagation conditions directly, update the reference signal pattern or symbol prefix configuration, and then send a request to the UE to send subsequent reference signals or data communications based on the updated configuration.

CROSS REFERENCES

The present Application for Patent claims priority to U.S. ProvisionalPatent Application No. 62/380,356 by Akkarakaran, et al., entitled“Adapting to Delay Spread Variation in MMW Systems,” filed Aug. 26,2016, assigned to the assignee hereof.

BACKGROUND

The following relates generally to wireless communication, and morespecifically to adapting to delay spread variation in wirelesscommunication systems.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems, (e.g., a Long Term Evolution(LTE) system). A wireless multiple-access communications system mayinclude a number of base stations, each simultaneously supportingcommunication for multiple communication devices, which may be otherwiseknown as user equipment (UE).

Some wireless communication systems may operate in millimeter wavespectrum. Millimeter wave communication may be sensitive to channelconditions such as frequency selectivity due to multipath propagation.Some wireless systems using millimeter wave communication may use analogbeamforming to improve signal quality and reduce path loss. Somebeamforming configurations may impact a typical channel delay spread formillimeter wave communication systems. Beamforming may use either anarrow transmit beam or broad transmit beam based on the channelconditions. For example, a broad transmit beam may improve channelquality by using multiple reflected paths. However, using the broadtransmit beam may use additional multipath and increase the delay spreadwhen compared to a narrow beam.

SUMMARY

A user equipment (UE) and base station may dynamically update areference signal pattern, a symbol prefix configuration, or both basedon channel propagation conditions such as a delay spread, multipathpropagation, or frequency selectivity. In some cases, the UE may measurethe channel propagation conditions and send an indication to the basestation. The base station may then update the reference signal patternor symbol prefix configuration accordingly, and send an indication ofthe new configuration to the UE. In some cases, i.e., for uplinkcommunications, the base station may measure the channel propagationconditions directly, update the reference signal pattern or symbolprefix configuration, and then send a request to the UE to sendsubsequent reference signals or data communications based on the updatedconfiguration. Updating a symbol prefix configuration may includeupdating a cyclic prefix configuration or a guard intervalconfiguration.

A method of wireless communication is described. The method may includeidentifying one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter, transmitting an indication of the oneor more propagation channel measurement parameters to a base station,receiving a configuration message from the base station in response totransmitting the indication of the one or more propagation channelmeasurement parameters, and updating a reference signal pattern or asymbol prefix configuration based on the configuration message.

An apparatus for wireless communication is described. The apparatus mayinclude means for identifying one or more propagation channelmeasurement parameters including a delay spread parameter, a multipathfading parameter, or a frequency selectivity parameter, means fortransmitting an indication of the one or more propagation channelmeasurement parameters to a base station, means for receiving aconfiguration message from the base station in response to transmittingthe indication of the one or more propagation channel measurementparameters, and means for updating a reference signal pattern or asymbol prefix configuration based on the configuration message.

Another apparatus for wireless communication is described. The apparatusmay include a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe operable to cause the processor to identify one or more propagationchannel measurement parameters including a delay spread parameter, amultipath fading parameter, or a frequency selectivity parameter,transmit an indication of the one or more propagation channelmeasurement parameters to a base station, receive a configurationmessage from the base station in response to transmitting the indicationof the one or more propagation channel measurement parameters, andupdate a reference signal pattern or a symbol prefix configuration basedon the configuration message.

A non-transitory computer readable medium for wireless communication isdescribed. The non-transitory computer-readable medium may includeinstructions operable to cause a processor to identify one or morepropagation channel measurement parameters including a delay spreadparameter, a multipath fading parameter, or a frequency selectivityparameter, transmit an indication of the one or more propagation channelmeasurement parameters to a base station, receive a configurationmessage from the base station in response to transmitting the indicationof the one or more propagation channel measurement parameters, andupdate a reference signal pattern or a symbol prefix configuration basedon the configuration message.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving one or more referencesignals based on the updated reference signal pattern.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the reference signal patternincludes a pattern for a channel state information reference signal(CSI-RS), a cell specific reference signal (CRS), a demodulationreference signal (DMRS), a beamforming reference signal (BRS), abeamforming measurement reference signal (MRS), or a sounding referencesignal (SRS).

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving a data communication fromthe base station based on the updated reference signal pattern or symbolprefix configuration.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the symbol prefixconfiguration includes an orthogonal frequency division multiplexing(OFDM) cyclic prefix configuration, a single carrier frequency divisionmultiplexing (SC-FDM) cyclic prefix configuration, or an SC-FDM guardinterval configuration.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving a broadcast systeminformation message or a radio resource control (RRC) message, where thereference signal pattern or the symbol prefix configuration may beupdated based on the broadcast system information message or the RRCmessage.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the configuration messageincludes a physical downlink control (PDCCH) message. In some examplesof the method, apparatus, and non-transitory computer-readable mediumdescribed above, the PDCCH message includes a common PDCCH message. Insome examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the PDCCH message includes anenhanced frequency or transmit power PDCCH message.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for identifying a coordinatedmultipoint (CoMP) configuration, a single-input multiple-output (SIMO)configuration, a multiple-input multiple-output (MIMO) configuration oradditional downlink control information, where the reference signalpattern or the symbol prefix configuration may be updated based on theCoMP configuration, the SIMO configuration, the MIMO configuration, orthe additional downlink control information.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the indication may betransmitted based on a periodic reporting configuration. Some examplesof the method, apparatus, and non-transitory computer-readable mediumdescribed above may further include processes, features, means, orinstructions for receiving a request to transmit the indication of theone or more propagation channel measurement parameters from the basestation, where the indication may be transmitted based on the request.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the symbol prefixconfiguration includes a set of cyclic prefix durations associated witha set of symbol periods of a subframe or a plurality of symbol periodsof a slot, or a combination thereof. In some examples of the method,apparatus, and non-transitory computer-readable medium described above,the configuration message includes a mapping between a subframe numberand a cyclic prefix duration, or a mapping between a slot number and thecyclic prefix duration, and where the symbol prefix configuration may beupdated based on the mapping and the subframe number or the mapping andthe slot number.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the SC-FDM guard intervalconfiguration includes an indication of a number of zeroes to beappended or prepended to a data symbol prior to a discrete Fouriertransform spreading. In some examples, the symbol prefix configurationmay include the guard interval configuration. In some examples of themethod, apparatus, and non-transitory computer-readable medium describedabove, the configuration message includes a combined indication of thereference signal pattern and the symbol prefix configuration.

A method of wireless communication is described. The method may includereceiving an indication of one or more propagation channel measurementparameters from a UE, the one or more propagation channel measurementparameters including a delay spread parameter, a multipath fadingparameter, or a frequency selectivity parameter, updating a referencesignal pattern or a symbol prefix configuration based on the indicationof the one or more propagation channel measurement parameters, andtransmitting a configuration message to the UE in response to receivingthe indication of the one or more propagation channel measurementparameters, the configuration message including an indication of theupdated reference signal pattern or symbol prefix configuration.

An apparatus for wireless communication is described. The apparatus mayinclude means for receiving an indication of one or more propagationchannel measurement parameters from a UE, the one or more propagationchannel measurement parameters including a delay spread parameter, amultipath fading parameter, or a frequency selectivity parameter, meansfor updating a reference signal pattern or a symbol prefix configurationbased on the indication of the one or more propagation channelmeasurement parameters, and means for transmitting a configurationmessage to the UE in response to receiving the indication of the one ormore propagation channel measurement parameters, the configurationmessage including an indication of the updated reference signal patternor symbol prefix configuration.

Another apparatus for wireless communication is described. The apparatusmay include a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe operable to cause the processor to receive an indication of one ormore propagation channel measurement parameters from a UE, the one ormore propagation channel measurement parameters including a delay spreadparameter, a multipath fading parameter, or a frequency selectivityparameter, update a reference signal pattern or a symbol prefixconfiguration based on the indication of the one or more propagationchannel measurement parameters, and transmit a configuration message tothe UE in response to receiving the indication of the one or morepropagation channel measurement parameters, the configuration messageincluding an indication of the updated reference signal pattern orsymbol prefix configuration.

A non-transitory computer readable medium for wireless communication isdescribed. The non-transitory computer-readable medium may includeinstructions operable to cause a processor to receive an indication ofone or more propagation channel measurement parameters from a UE, theone or more propagation channel measurement parameters including a delayspread parameter, a multipath fading parameter, or a frequencyselectivity parameter, update a reference signal pattern or a symbolprefix configuration based on the indication of the one or morepropagation channel measurement parameters, and transmit a configurationmessage to the UE in response to receiving the indication of the one ormore propagation channel measurement parameters, the configurationmessage including an indication of the updated reference signal patternor symbol prefix configuration.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for transmitting one or more referencesignals based on the updated reference signal pattern.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for transmitting a data communicationto the UE based on the updated reference signal pattern or symbol prefixconfiguration.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for transmitting a broadcast systeminformation message or a RRC message, where the reference signal patternor the symbol prefix configuration may be updated based on the broadcastsystem information message or the RRC message.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the configuration messageincludes a PDCCH message. In some examples of the method, apparatus, andnon-transitory computer-readable medium described above, the PDCCHmessage includes a common PDCCH message. In some examples of the method,apparatus, and non-transitory computer-readable medium described above,the PDCCH message includes an enhanced frequency or receive power PDCCHmessage.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for transmitting an additionalconfiguration message using a different beamforming direction, where theadditional configuration message includes an indication of the updatedreference signal pattern or symbol prefix configuration.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for identifying a CoMP configuration, aSIMO configuration, a MIMO configuration or additional downlink controlinformation, where the reference signal pattern or the symbol prefixconfiguration may be updated based on the CoMP configuration, the SIMOconfiguration, the MIMO configuration, or the additional downlinkcontrol information.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for transmitting a request for the UEto transmit the indication of the one or more propagation channelmeasurement parameters, where the indication may be received based onthe request.

A method of wireless communication is described. The method may includereceiving a reference signal request from a base station based on one ormore propagation channel measurement parameters, the one or morepropagation channel measurement parameters including a delay spreadparameter, a multipath fading parameter, or a frequency selectivityparameter, updating a reference signal pattern based on the referencesignal request, and transmitting an uplink message to the base stationbased on the updated reference signal pattern.

An apparatus for wireless communication is described. The apparatus mayinclude means for receiving a reference signal request from a basestation based on one or more propagation channel measurement parameters,the one or more propagation channel measurement parameters including adelay spread parameter, a multipath fading parameter, or a frequencyselectivity parameter, means for updating a reference signal patternbased on the reference signal request, and means for transmitting anuplink message to the base station based on the updated reference signalpattern.

Another apparatus for wireless communication is described. The apparatusmay include a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe operable to cause the processor to receive a reference signal requestfrom a base station based on one or more propagation channel measurementparameters, the one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter, update a reference signal pattern basedon the reference signal request, and transmit an uplink message to thebase station based on the updated reference signal pattern.

A non-transitory computer readable medium for wireless communication isdescribed. The non-transitory computer-readable medium may includeinstructions operable to cause a processor to receive a reference signalrequest from a base station based on one or more propagation channelmeasurement parameters, the one or more propagation channel measurementparameters including a delay spread parameter, a multipath fadingparameter, or a frequency selectivity parameter, update a referencesignal pattern based on the reference signal request, and transmit anuplink message to the base station based on the updated reference signalpattern.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the uplink message includes aSRS or a beamforming MRS.

A method of wireless communication is described. The method may includeidentifying one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter, updating a reference signal pattern ora symbol prefix configuration based on the one or more propagationchannel measurement parameters, transmitting a reference signal requestto a UE, where the reference signal requests indicates the updatedreference signal pattern or symbol prefix configuration, and receivingan uplink message from the UE in response to the reference signalrequest, where the uplink message is based on the reference signalpattern or the symbol prefix configuration.

An apparatus for wireless communication is described. The apparatus mayinclude means for identifying one or more propagation channelmeasurement parameters including a delay spread parameter, a multipathfading parameter, or a frequency selectivity parameter, means forupdating a reference signal pattern or a symbol prefix configurationbased on the one or more propagation channel measurement parameters,means for transmitting a reference signal request to a UE, where thereference signal requests indicates the updated reference signal patternor symbol prefix configuration, and means for receiving an uplinkmessage from the UE in response to the reference signal request, wherethe uplink message is based on the reference signal pattern or thesymbol prefix configuration.

Another apparatus for wireless communication is described. The apparatusmay include a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe operable to cause the processor to identify one or more propagationchannel measurement parameters including a delay spread parameter, amultipath fading parameter, or a frequency selectivity parameter, updatea reference signal pattern or a symbol prefix configuration based on theone or more propagation channel measurement parameters, transmit areference signal request to a UE, where the reference signal requestsindicates the updated reference signal pattern or symbol prefixconfiguration, and receive an uplink message from the UE in response tothe reference signal request, where the uplink message is based on thereference signal pattern or the symbol prefix configuration.

A non-transitory computer readable medium for wireless communication isdescribed. The non-transitory computer-readable medium may includeinstructions operable to cause a processor to identify one or morepropagation channel measurement parameters including a delay spreadparameter, a multipath fading parameter, or a frequency selectivityparameter, update a reference signal pattern or a symbol prefixconfiguration based on the one or more propagation channel measurementparameters, transmit a reference signal request to a UE, where thereference signal requests indicates the updated reference signal patternor symbol prefix configuration, and receive an uplink message from theUE in response to the reference signal request, where the uplink messageis based on the reference signal pattern or the symbol prefixconfiguration.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the uplink message includes aSRS or a beamforming MRS. In some examples of the method, apparatus, andnon-transitory computer-readable medium described above, the one or morepropagation channel measurement parameters may be based on a channelreciprocity of a time division duplexing (TDD) configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate examples of systems for wireless communicationthat supports adapting to delay spread variation in wirelesscommunication systems in accordance with aspects of the presentdisclosure.

FIGS. 3 and 4 illustrate examples of process flows that supportsadapting to delay spread variation in wireless communication systems inaccordance with aspects of the present disclosure.

FIGS. 5 through 7 show block diagrams of a device that supports adaptingto delay spread variation in wireless communication systems inaccordance with aspects of the present disclosure.

FIG. 8 illustrates a block diagram of a system including a userequipment (UE) that supports adapting to delay spread variation inwireless communication systems in accordance with aspects of the presentdisclosure.

FIGS. 9 through 11 show block diagrams of a device that supportsadapting to delay spread variation in wireless communication systems inaccordance with aspects of the present disclosure.

FIG. 12 illustrates a block diagram of a system including a base stationthat supports adapting to delay spread variation in wirelesscommunication systems in accordance with aspects of the presentdisclosure.

FIGS. 13 through 18 illustrate methods for adapting to delay spreadvariation in wireless communication systems in accordance with aspectsof the present disclosure.

DETAILED DESCRIPTION

A user equipment (UE) and base station (e.g., UEs and base stationoperating in a wireless communication spectrum) may dynamically update areference signal density, a cyclic prefix configuration, or both basedon channel propagation conditions such as a delay spread, multipathpropagation, or frequency selectivity, for example the wirelesscommunication spectrum may be millimeter wave (mmW) spectrum, sub-6 GHzspectrum, among others. The UE and base station may use referencesignals for channel quality estimation associated with differentfrequency ranges. That is, the reference signals may span a wide band offrequencies to enable estimation of frequency selective channels, wherethe channel may not have sufficient channel quality at some frequencies.

Thus, the UE or base station may determine a multipath delay spreadbased on the difference of a maximum and minimum delay of all the paths.The base station may semi-statically or dynamically adjust a referencesignal configuration to enhance channel quality based on the delayspread, or the base station may configure the UE to adjust the referencesignal configuration. The UE or base station may identify propagationchannel measurement parameters and determine a reference signalconfiguration based on the parameters. For example, the configurationmay include a reference signal density or pattern. Furthermore, channelsexperiencing multipath interference may have increased inter-symbolinterference. Adjusting the cyclic prefix or a guard period to theduration of the delay spread may reduce the inter-symbol interference. Acyclic prefix and reference signal density or pattern may be configuredjointly to reduce the signaling overhead if the configurations arecorrelated. For example, some reference signal configurations mayimplicitly specify the cyclic prefix configuration.

Aspects of the disclosure are initially described in the context of awireless communications system. The wireless communication system maysupport for adapting to delay spread variation in wireless communicationsystems. Aspects of the disclosure are further illustrated by anddescribed with reference to apparatus diagrams, system diagrams, andflowcharts that relate to adapting to delay spread variation in wirelesscommunication systems. In some examples, wireless communication systemsmay be or include a mmW system.

FIG. 1 illustrates an example of a wireless communications system 100 inaccordance with various aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, UEs 115, and acore network 130. In some examples, the wireless communications system100 may be a LTE (or LTE-Advanced) network.

Wireless communication system 100 may operate in an ultra high frequency(UHF) frequency region using frequency bands from 700 MHz to 2600 MHz(2.6 GHz), although in some cases WLAN networks may use frequencies ashigh as 4 GHz. This region may also be known as the decimeter band,since the wavelengths range from approximately one decimeter to onemeter in length. UHF waves may propagate mainly by line of sight, andmay be blocked by buildings and environmental features. However, thewaves may penetrate walls sufficiently to provide service to UEs 115located indoors. Transmission of UHF waves is characterized by smallerantennas and shorter range (e.g., less than 100 km) compared totransmission using the smaller frequencies (and longer waves) of thehigh frequency (HF) or very high frequency (VHF) portion of thespectrum. In some cases, wireless communication system 100 may alsoutilize extremely high frequency (EHF) portions of the spectrum (e.g.,from 30 GHz to 300 GHz). This region may also be known as the millimeterband, since the wavelengths range from approximately one millimeter toone centimeter in length. Thus, EHF antennas may be even smaller andmore closely spaced than UHF antennas. In some cases, this mayfacilitate use of antenna arrays within a UE 115 (e.g., for directionalbeamforming). However, EHF transmissions may be subject to even greateratmospheric attenuation and shorter range than UHF transmissions.

Wireless communications system 100 may support communications (e.g.,such as communications using mmW spectrum, sub-6 GHz spectrum, etc.)between UEs 115 and base stations 105. Devices (e.g., UEs 115 and basestation 105) operating in a wireless communication spectrum may havemultiple antennas to allow beamforming. That is, a base station 105 mayuse multiple antennas or antenna arrays to conduct beamformingoperations for directional communications with a UE 115. Beamforming(which may also be referred to as spatial filtering) is a signalprocessing technique that may be used at a transmitter (e.g. a basestation 105) to shape and/or steer an overall antenna beam in thedirection of a target receiver (e.g. a UE 115). This may be achieved bycombining elements in an antenna array in such a way that transmittedsignals at particular angles experience constructive interference whileothers experience destructive interference. Multiple-inputmultiple-output (MIMO) wireless systems use a transmission schemebetween a transmitter (e.g. a base station) and a receiver (e.g. a UE115), where both transmitter and receiver are equipped with multipleantennas. Some portions of wireless communications system 100 may usebeamforming. For example, base station 105 may have an antenna arraywith a number of rows and columns of antenna ports that the base station105 may use for beamforming in its communication with UE 115. Signalsmay be transmitted multiple times in different directions (e.g., eachtransmission may be beamformed differently). A receiving device (e.g., aUE 115) may try multiple beams (e.g., antenna subarrays) while receivingthe synchronization signals.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Each base station 105 may providecommunication coverage for a respective geographic coverage area 110.Communication links 125 shown in wireless communications system 100 mayinclude UL transmissions from a UE 115 to a base station 105, or DLtransmissions, from a base station 105 to a UE 115. UEs 115 may bedispersed throughout the wireless communications system 100, and each UE115 may be stationary or mobile. A UE 115 may also be referred to as amobile station, a subscriber station, a remote unit, a wireless device,an access terminal (AT), a handset, a user agent, a client, or liketerminology. A UE 115 may also be a cellular phone, a wireless modem, ahandheld device, a personal computer, a tablet, a personal electronicdevice, an MTC device, etc.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., S1, etc.). Base stations105 may communicate with one another over backhaul links 134 (e.g., X2,etc.) either directly or indirectly (e.g., through core network 130).Base stations 105 may perform radio configuration and scheduling forcommunication with UEs 115, or may operate under the control of a basestation controller (not shown). In some examples, base stations 105 maybe macro cells, small cells, hot spots, or the like. Base stations 105may also be referred to as eNodeBs (eNBs) 105.

In some cases, the antennas of a base station 105 or UE 115 may belocated within one or more antenna arrays. One or more base stationantennas or antenna arrays may be collocated at an antenna assembly,such as an antenna tower. In some cases, antennas or antenna arraysassociated with a base station 105 may be located in diverse geographiclocations. A base station 105 may multiple use antennas or antennaarrays to conduct beamforming operations for directional communicationswith a UE 115.

A UE 115 or base station 105 may be configured for MIMO transmission.MIMO is a transmission scheme between a transmitter and a receiver bothequipped with multiple antennas. A UE 115 may be configured tocollaboratively communicate with multiple eNBs 105 through, for example,MIMO, Coordinated Multi-Point (CoMP), or other schemes. MIMO techniquesuse multiple antennas on the base stations 105 or multiple antennas onthe UE 115 to take advantage of multipath environments to transmitmultiple data streams. CoMP includes techniques for dynamic coordinationof transmission and reception by a number of eNBs to improve overalltransmission quality for UEs 115 as well as increasing network andspectrum utilization.

Multipath propagation is a radio condition caused by RF signals takingdifferent paths from the transmitter to the receiver and subsequentlyinterfering with each other. For example, it may be caused by differentcopies of a wireless signal reaching a receiver via different paths withvarying path lengths. The different path lengths may be based on, forexample, atmospheric reflection and refraction, or reflection frombuildings, water, and other surfaces. Multipath propagation may resultin a time delay (or a phase shift) for one copy of a signal, which causeconstructive or destructive interference (between consecutive symbols,inter-symbol interference (ISI), or within a single symbol). A guardinterval (GI) (which may include a cyclic prefix) may be prepended orappended to transmissions to enable mitigation of the effects of channelspreading caused by multipath propagation.

In some examples, time intervals may be expressed in multiples of abasic time unit (e.g., the sampling period, T_(s)=1/30,720,000 seconds).Time resources may be organized according to radio frames of length of10 ms (T_(f)=307200T_(s)), which may be identified by an SFN rangingfrom 0 to 1023. Each frame may include ten 1 ms subframes numbered from0 to 9. A subframe may be further divided into two 0.5 ms slots, each ofwhich contains 6 or 7 modulation symbol periods (depending on the lengthof the cyclic prefix prepended to each symbol). That is, a cyclic prefixmay be appended to the beginning of each symbol to prevent inter-symbolinterference.

In some examples, for some wave forms (such as single carrier frequencydivision multiplexing (SC-FDM) waveforms) a guard interval or zero tailconsisting of one or more zeros prepended and/or appended to a datasequence may be used instead of or in addition to a cyclic prefix.Excluding the cyclic prefix, each symbol contains 2048 sample periods.In some cases the subframe may be the smallest scheduling unit of time,also known as a TTI. In other cases, a TTI may be shorter than asubframe or may be dynamically selected (e.g., in short TTI bursts or inselected component carriers using short TTIs). In some examples, the TTImay be a slot or a mini-slot.

A base station 105 may insert periodic pilot symbols such as a cellspecific reference signal (CRS) to aid UEs 115 in channel estimation andcoherent demodulation. CRS may include one of 504 different cellidentities. They may be modulated using QPSK and power boosted (e.g.,transmitted at 6 dB higher than the surrounding data elements) to makethem resilient to noise and interference. CRS may be embedded in 4 to 16resource elements in each resource block based on the number of antennaports or layers (up to 4) of the receiving UEs 115. In addition to CRS,which may be utilized by all UEs 115 in the coverage area 110 of thebase station 105, a demodulation reference signal (DMRS) may be directedtoward specific UEs 115 and may be transmitted on resource blocksassigned to those UEs 115. DMRS may include signals on 6 resourceelements in each resource block in which they are transmitted. The DMRSfor different antenna ports may each utilize the same 6 resourceelements, and may be distinguished using different orthogonal covercodes (e.g., masking each signal with a different combination of 1 or −1in different resource elements). In some cases, two sets of DMRS may betransmitted in adjoining resource elements. In some cases, additionalreference signals known as channel state information reference signals(CSI-RS) may be included to aid in generating CSI. On the uplink (UL), aUE 115 may transmit a combination of periodic sounding reference signal(SRS) and UL DMRS for link adaptation and demodulation, respectively. Insome cases, the reference signal density or pattern may depend onchannel conditions such as frequency selectivity, multipath propagation,or delay spread.

Thus, a UE 115 and base station 105 may dynamically update a referencesignal pattern, a symbol prefix configuration, or both based on channelpropagation conditions such as a delay spread, multipath propagation, orfrequency selectivity. In some cases, the UE 115 may measure the channelpropagation conditions and send an indication to the base station 105.The base station 105 may then update the reference signal pattern orsymbol prefix configuration accordingly, and send an indication of thenew configuration to the UE 115. In some examples, the symbol prefixconfiguration may include a guard interval configuration. In some cases,i.e., for uplink communications, the base station 105 may measure thechannel propagation conditions directly, update the reference signalpattern or symbol prefix configuration, and then send a request to theUE 115 to send subsequent reference signals or data communications basedon the updated configuration.

FIG. 2 illustrates an example of a wireless communication system 200that supports adapting to delay spread variation in wirelesscommunication systems. In some cases, wireless communication system 200may represent aspects of techniques performed by a UE 115 or basestation 105 as described with reference to FIG. 1. The wirelesscommunication system 200 may include UE 115-a and base station 105-a,which may respectively be examples of a UE 115 and a base station 105 ofFIG. 1.

UE 115-a and base station 105-a may set a reference signal density andsymbol prefix configuration based on channel conditions. UE 115-a andbase station 105-a may use reference signals for channel qualityestimation. In some examples, UE 115-a and base station 105-a maycommunicate using an orthogonal frequency division multiplexing (OFDM)waveform. The reference signals may span a wide band of frequencies toenable estimation of frequency selective channels, where the channel maynot have sufficient channel quality at some frequencies. UE 115-a orbase station 105-a may determine a multipath delay spread based on thedifference of a maximum and minimum delay of all the paths. Base station105-a may semi-statically or dynamically adjust a reference signalconfiguration to enhance channel quality based on the delay spread, orbase station 105-a may configure UE 115-a to adjust the reference signalconfiguration. Furthermore, channels experiencing multipath interferencemay have increased inter-symbol interference. Adjusting the cyclicprefix or guard period to the duration of the delay spread may reducethe inter-symbol interference. However, changing the cyclic prefix maychange the overall symbol duration or number of symbols in the slot orsubframe, which may affect the slot or subframe timing.

A reference signal density of a channel may be adjustable based onchannel conditions. For example, a channel used for millimeter wavecommunication may use an adjustable reference signal configuration. Thechannel may be frequency selective due to multipath interference in thechannel, and the channel may not have sufficient channel quality at somefrequencies. The frequency selectivity of the channel may be based on amultipath delay spread, which may be determined based on the differenceof a maximum and minimum delay of all paths. The frequency selectivitymay also be based on the channel's impulse response (e.g., the full setof path delays, gains and phases). Therefore, the frequency selectivityof the channel may not be directly proportional with the multipathdelay. However, a low delay spread (e.g., a single path channel) maytranslate to a low frequency selectivity, which may enable a referencesignal to be placed more sparsely in frequency and reduce a referencesignal overhead. The correlation of low delay spread to low frequencyselectivity may be appropriate for determining a pattern (e.g.,placement) of channel estimation for data demodulation (e.g., DMRS orreference signals used for noise compensation) as well as those used forCQI (e.g., CSI-RS) and beam-related measurements.

A reference signal configuration may be dynamically or semi-staticallydetermined based on propagation channel measurement parameters.Propagation channel measurement parameters may include CSI-RS densityand a DMRS pattern. A set of possible values of the propagation channelmeasurement parameters may be defined, and the parameters used for aslot or subframe may be selected based on information in a schedulinggrant. In one example, the information may be a set of bits reserved forindicating the desired set of propagation channel measurement parametersor an indirect indication based on other parameters of the grant orbroadcast system information (e.g., system information blocks (SIBs) orradio resource control (RRC) messages). In another example, a DMRSpattern may depend on whether single-input, multiple-output (SIMO) orMIMO transmissions are used, which may be based on the scheduling grant.The DMRS pattern may also be based on an explicit indication viareserved bits in the scheduling grant.

UE 115-a may report propagation channel measurement parameters to basestation 105-a. UE 115-a may periodically report information such asdelay-spread, a number of multipaths, an observed frequency selectivity(e.g., based on reference signal measurements) to base station 105-a tohelp base station 105-a determine preferred settings of the propagationchannel measurement parameters for UE 115-a. Base station 105-a may thentransmit a configuration message to UE 115-a in response to theparameters. In other examples, UE 115-a may also directly request aparticular set of propagation channel measurement parameters. Basestation 105-a may decide propagation channel measurement parametersbased on the reports from UE 115-a or based on uplink channelmeasurements made at base station 105-a. The measurements may be basedon channel reciprocity for TDD systems. For a requested referencesignal, propagation channel measurement parameters may be included in arequest to transmit the reference signal. For example, for uplinksounding reference signal transmissions made by UE 115-a in response toa request from base station 105-a, the SRS density may be included inthe request. Similarly, if UE 115-a requests a mobile relay stationtraining, the measurement reference signal (MRS) density may be includedin the request

Base station 105-a may adjust a cyclic prefix or guard period based on adelay spread. Adjusting the cyclic prefix or guard period may reduce theinter-symbol interference. The cyclic prefix for an OFDM based waveformmay be used for frequency-domain equalization of multipath channels. Thecyclic prefix may be at least as long the channel delay spread to avoidcausing inter-symbol interference. However, changing the cyclic prefixmay change the overall OFDM symbol period duration, which may alter theslot or subframe timing. Multiple cyclic prefix durations may bepredefined, and each predefined duration may align with a slot orsubframe by changing a number of OFDM symbols in the slot or subframe.

The adjusted cyclic prefix or guard period duration for a slot orsubframe may be indicated in control signaling at the beginning of theslot or subframe. OFDM symbols in the beginning of the slot or subframemay carry control information (e.g., PDCCH) and may indicate whichcyclic prefix configuration to use for the rest of the slot or subframe.The slot or subframe may have a fixed cyclic prefix length. If the slotor subframe has a variable cyclic prefix length, a more complex multiplecyclic prefix hypothesis blind decoding of the control information maybe used to determine the cyclic prefix. Since all UEs 115 usingresources in the slot or subframe use the same cyclic prefixconfiguration, a broadcast message may be used in the initial OFDMsymbols. In some examples, the broadcast message may be read by all UEs115 instead of signaling the same information in every control channelgrant. In wireless systems using millimeter wave transmission, becausebeamforming is used to reach the cell edge, the broadcast may bescheduled to ensure that all UEs 115 receiving the same slot or subframereceive it based on a similar transmit beam direction from base station105-a. In other examples, a broadcast message may also be allocatedadditional frequency and power resources.

Symbol prefix configurations may be mapped to a slot or subframe number.Base station 105-a may schedule UE 115-a based on an estimated cyclicprefix length requirement of UE 115-a. This may avoid dynamicallysignaling the cyclic prefix, but may result in increased schedulingcomplexity and reduced flexibility in scheduling. The flexibilityreduction may be mitigated by semi-statically adapting the slot orsubframe to cyclic prefix configuration mapping (e.g., configuring moreslots or subframes for a shorter cyclic prefix if users have low delayspreads). For a zero tailed or guard interval based SC-FDM waveform, aguard period, prior to discrete Fourier transform (DFT) spreading or inan inverse fast

Fourier transform (IFFT) duration, may be used instead of a cyclicprefix. Changing the length of the guard interval may not change theSC-FDM symbol size. Therefore, using the guard interval may allow for amore continuous adaptation of the guard interval length withoutadditional configuration to align to a slot duration or subframeduration for each for each choice of guard interval. A broadcastingconfiguration or a mapping configuration, similar to configurations usedfor a cyclic prefix, may also be used for a guard period. Furthermore,different UEs 115 using resources within a common slot or subframe mayhave different guard interval lengths. In some examples, an SC-FDMwaveform may be referred to as a DFT-spread OFDM waveform orDFT-precoded OFDM waveform.

Symbol prefix and reference signal density may be configured jointly toreduce the signaling overhead if the configurations are correlated. Forexample, if a symbol prefix configuration (e.g., for a cyclic prefix ora guard interval) is signaled in PDCCH, then joint signaling of theconfiguration with a propagation channel measurement parameter mayreduce signaling overhead. For example, low delay spreads may beassociated with a low cyclic prefix and low reference signal density, sothe signaling may not have provision for all combinations of cyclicprefix (e.g., high/low) and reference signal density (e.g., low/high).If the wireless system uses propagation channel measurement parameters,some transmission modes may implicitly specify the symbol prefixconfiguration. For example, if UE 115-a receives data simultaneouslyfrom multiple base stations 105 (e.g., for downlink CoMP transmission),there may be a higher chance of a higher delay spread. Therefore, ahigher cyclic prefix configuration may be implicitly determined insteadof signaling the cyclic prefix separately.

FIG. 3 illustrates an example of a process flow 300 for adapting todelay spread variation in wireless communication systems. Process flow300 may include UE 115-b and base station 105-b, which may be respectiveexamples of a UE 115 and base station 105 as described herein withreference to FIGS. 1-2. Process flow 300 may be an example of a downlinkadaptation to delay spread variation in wireless communication systems.In some examples, wireless communication systems may be or include a mmWsystem.

At step 305, UE 115-b may determine propagation channel measurementparameters. UE 115-b may monitor downlink transmission to determine theparameters. The parameters may include a delay spread parameter, amultipath fading parameter, and a frequency selectivity parameter.

At step 310, UE 115-b may transmit an indication of one or more of theparameters to base station 105-b. The indication may be transmittedbased on a period reporting configuration.

At step 315, base station 105-b may determine a configuration forwireless communication. For example, the configuration may relate to areference signal pattern or a symbol prefix configuration. The referencesignal pattern may include a pattern for a CSI-RS, a CRS, a DMRS, abeamforming reference signal (BRS), an MRS, or an RS. The symbol prefixconfiguration may include an OFDM cyclic prefix configuration, an SC-FDMcyclic prefix configuration, or an SC-FDM guard interval configuration.The symbol prefix configuration may also include multiple cyclic prefixdurations associated with multiple symbol periods of a slot or subframe.

At step 320, base station 105-b may transmit a configuration message toUE 115-b. The configuration message may be transmitted in response to UE115-b transmitting the propagation channel measurement parameters andmay include the symbol prefix configuration or reference signal patterndetermined in step 315. The configuration message may include a mappingbetween a slot number or subframe number and a cyclic prefix duration,where the symbol prefix configuration is updated based on the mapping.In some examples, the configuration may not itself include the mapping,but the mapping may be configured by an RRC message and the slot numberor subframe number of the configuration message. The configurationmessage may include a combination indication of the reference signalpattern and the symbol prefix configuration.

At step 325, UE 115-b may update a reference symbol configuration orsymbol prefix configuration. UE 115-b may update the reference signalpattern or symbol prefix configuration based on the configurationmessage. At step 330, UE 115-b and base station 105-b may communicateusing the updated reference symbol configuration or symbol prefixconfiguration.

FIG. 4 illustrates an example of a process flow 400 for adapting todelay spread variation in wireless communication systems. Process flow300 may include UE 115-c and base station 105-c, which may be respectiveexamples of a UE 115 and base station 105 as described herein withreference to FIGS. 1-3. Process flow 300 may be an example of an uplinkadaptation to delay spread variation in wireless communication systems.In some examples, wireless communication systems may be or include a mmWsystem.

At step 405, base station 105-c may determine propagation channelmeasurement parameters. The propagation channel measurement parametersmay include a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter.

At step 410, base station 105-c may determine an updated configurationfor a reference signal pattern or symbol prefix configuration. Basestation 105-c may update the reference signal pattern or symbol prefixconfiguration based on the propagation channel measurement parameters.The reference signal pattern may include a pattern for a CSI-RS, a CRS,a DMRS, a BRS, an MRS, or an RS. The symbol prefix configuration mayinclude an OFDM cyclic prefix configuration, an SC-FDM cyclic prefixconfiguration, or an SC-FDM guard interval configuration. The symbolprefix configuration may also include multiple cyclic prefix durationsassociated with multiple symbol periods of a slot or subframe.

At step 415, base station 105-c may transmit a configuration message toUE 115-c. The configuration message may include the symbol prefixconfiguration or reference signal pattern determined in step 410. Theconfiguration message may include a mapping between a subframe numberand a cyclic prefix duration, or a mapping between a slot number and thecyclic prefix duration, where the symbol prefix configuration is updatedbased on the mapping and the subframe number or the mapping and the slotnumber. The configuration message may include a combination indicationof the reference signal pattern and the symbol prefix configuration.

At step 420, UE 115-c may update a reference symbol configuration orsymbol prefix configuration. UE 115-c may update the reference signalpattern or symbol prefix configuration based on the configurationmessage. At step 425, UE 115-c and base station 105-c may communicateusing the updated reference symbol configuration or symbol prefixconfiguration.

FIG. 5 shows a block diagram 500 of a device 505 that supports adaptingto delay spread variation in wireless communication systems inaccordance with various aspects of the present disclosure. Device 505may be an example of aspects of a UE 115 as described with reference toFIG. 1. Device 505 may include receiver 510, UE delay spread manager515, and transmitter 520. Device 505 may also include a processor. Eachof these components may be in communication with one another (e.g., viaone or more buses). In some examples, wireless communication systems maybe or include a mmW system.

Receiver 510 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to adapting todelay spread variation in wireless communication systems, etc.).Information may be passed on to other components of the device. Thereceiver 510 may be an example of aspects of the transceiver 835described with reference to FIG. 8. For example, receiver 510 mayreceive a data communication from a base station 105 based on an updatedreference signal pattern or symbol prefix configuration.

UE delay spread manager 515 may be an example of aspects of the UE delayspread manager 815 described with reference to FIG. 8. UE delay spreadmanager 515 may identify one or more propagation channel measurementparameters including a delay spread parameter, a multipath fadingparameter, or a frequency selectivity parameter, transmit an indicationof the one or more propagation channel measurement parameters to a basestation 105, receive a configuration message from the base station 105in response to transmitting the indication of the one or morepropagation channel measurement parameters, and update a referencesignal pattern or a symbol prefix configuration based on theconfiguration message.

UE delay spread manager 515 may also receive a reference signal requestfrom a base station 105 based on one or more propagation channelmeasurement parameters, the one or more propagation channel measurementparameters including a delay spread parameter, a multipath fadingparameter, or a frequency selectivity parameter and update a referencesignal pattern or a symbol prefix configuration based on the referencesignal request.

Transmitter 520 may transmit signals generated by other components ofthe device. In some examples, the transmitter 520 may be collocated witha receiver 510 in a transceiver module. For example, the transmitter 520may be an example of aspects of the transceiver 835 described withreference to FIG. 8. The transmitter 520 may include a single antenna,or it may include a set of antennas. For example, transmitter 520 maytransmit an uplink message to the base station 105 based on the updatedreference signal pattern or symbol prefix configuration. In some cases,the uplink message includes a SRS or a beamforming MRS.

FIG. 6 shows a block diagram 600 of a device 605 that supports adaptingto delay spread variation in wireless communication systems inaccordance with various aspects of the present disclosure. Device 605may be an example of aspects of a device 505 or a UE 115 as describedwith reference to FIGS. 1 and 5. Device 605 may include receiver 610, UEdelay spread manager 615, and transmitter 620. Device 605 may alsoinclude a processor. Each of these components may be in communicationwith one another (e.g., via one or more buses). In some examples,wireless communication systems may be or include a mmW system.

Receiver 610 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to adapting todelay spread variation in wireless communication systems, etc.).Information may be passed on to other components of the device. Thereceiver 610 may be an example of aspects of the transceiver 835described with reference to FIG. 8.

UE delay spread manager 615 may be an example of aspects of the UE delayspread manager 815 described with reference to FIG. 8. UE delay spreadmanager 615 may also include channel measurement component 625, channelmeasurement indication component 630, and dynamic configurationcomponent 635.

Channel measurement component 625 may identify one or more propagationchannel measurement parameters including a delay spread parameter, amultipath fading parameter, or a frequency selectivity parameter.Channel measurement indication component 630 may transmit an indicationof the one or more propagation channel measurement parameters to a basestation 105. In some cases, the indication is transmitted based on aperiodic reporting configuration.

Dynamic configuration component 635 may receive a configuration messagefrom the base station 105 in response to transmitting the indication ofthe one or more propagation channel measurement parameters, update areference signal pattern or a symbol prefix configuration based on theconfiguration message, receive a reference signal request from the basestation 105 based on one or more propagation channel measurementparameters, the one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter, update a reference signal pattern or asymbol prefix configuration based on the reference signal request, andidentify a CoMP configuration, a single-input multiple-output SIMOconfiguration, a MIMO configuration or additional downlink controlinformation, where the reference signal pattern or the symbol prefixconfiguration is updated based on the CoMP configuration, the SIMOconfiguration, the MIMO configuration, or the additional downlinkcontrol information.

In some cases, the configuration message includes a PDCCH message. Insome cases, the PDCCH message includes a common PDCCH message. In somecases, the PDCCH message includes an enhanced frequency or transmitpower PDCCH message. In some cases, the symbol prefix configurationincludes a set of cyclic prefix durations associated with a set ofsymbol periods of a subframe, or a set of symbol periods of a slot, or acombination thereof. In some cases, the configuration message includes amapping between a subframe number and a cyclic prefix duration, or amapping between a slot number and the cyclic prefix duration, and wherethe symbol prefix configuration is updated based on the mapping and thesubframe number or the mapping and the slot number.

In some cases, the SC-FDM guard interval configuration includes anindication of a number of zeroes to be appended or prepended to a datasymbol within an IFFT interval or prior to DFT spreading. In some cases,the configuration message includes a combined indication of thereference signal pattern and the symbol prefix configuration. In somecases, the symbol prefix configuration includes an OFDM cyclic prefixconfiguration, an SC-FDM cyclic prefix configuration, or an SC-FDM guardinterval configuration.

Transmitter 620 may transmit signals generated by other components ofthe device. In some examples, the transmitter 620 may be collocated witha receiver 610 in a transceiver module. For example, the transmitter 620may be an example of aspects of the transceiver 835 described withreference to FIG. 8. The transmitter 620 may include a single antenna,or it may include a set of antennas.

FIG. 7 shows a block diagram 700 of a UE delay spread manager 715 thatsupports adapting to delay spread variation in wireless communicationsystems in accordance with various aspects of the present disclosure.The UE delay spread manager 715 may be an example of aspects of a UEdelay spread manager 515, a UE delay spread manager 615, or a UE delayspread manager 815 described with reference to FIGS. 5, 6, and 8. The UEdelay spread manager 715 may include channel measurement component 720,channel measurement indication component 725, dynamic configurationcomponent 730, reference signal component 735, semi-static configurationcomponent 740, and channel measurement request component 745. Each ofthese modules may communicate, directly or indirectly, with one another(e.g., via one or more buses). In some examples, wireless communicationsystems may be or include a mmW system.

Channel measurement component 720 may identify one or more propagationchannel measurement parameters including a delay spread parameter, amultipath fading parameter, or a frequency selectivity parameter.Channel measurement indication component 725 may transmit an indicationof the one or more propagation channel measurement parameters to a basestation 105. In some cases, the indication is transmitted based on aperiodic reporting configuration.

Dynamic configuration component 730 may receive a configuration messagefrom the base station 105 in response to transmitting the indication ofthe one or more propagation channel measurement parameters, update areference signal pattern or a symbol prefix configuration based on theconfiguration message, receive a reference signal request from the basestation 105 based on one or more propagation channel measurementparameters, the one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter, update a reference signal pattern or asymbol prefix configuration based on the reference signal request, andidentify a CoMP configuration, a SIMO configuration, a MIMOconfiguration or additional downlink control information.

Reference signal component 735 may receive one or more reference signalsbased on the updated reference signal pattern. In some cases, thereference signal pattern includes a pattern for a CSI-RS, a CRS, a DMRS,a BRS, a beamforming MRS, or a SRS.

Semi-static configuration component 740 may receive a broadcast systeminformation message or a radio resource control (RRC) message, where thereference signal pattern or the symbol prefix configuration are updatedbased on the broadcast system information message or the RRC message.The reference signal pattern or the symbol prefix configuration may beupdated based on a mapping between the reference signal pattern orsymbol prefix configuration and a subframe number or a mapping between aslot number and the cyclic prefix duration. In some cases, the mappingmay be previously configured by the RRC message.

Channel measurement request component 745 may receive a request totransmit the indication of the one or more propagation channelmeasurement parameters from the base station 105, where the indicationis transmitted based on the request.

FIG. 8 shows a diagram of a system 800 including a device 805 thatsupports adapting to delay spread variation in wireless communicationsystems in accordance with various aspects of the present disclosure.Device 805 may be an example of or include the components of device 505,device 605, or a UE 115 as described above, e.g., with reference toFIGS. 1, 5 and 6. Device 805 may include components for bi-directionalvoice and data communications including components for transmitting andreceiving communications, including UE delay spread manager 815,processor 820, memory 825, software 830, transceiver 835, antenna 840,and I/O controller 845. These components may be in electroniccommunication via one or more busses (e.g., bus 810). Device 805 maycommunicate wirelessly with one or more base stations 105. In someexamples, wireless communication systems may be or include a mmW system.

Processor 820 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a digital signal processor (DSP), a centralprocessing unit (CPU), a microcontroller, an application-specificintegrated circuit (ASIC), an field-programmable gate array (FPGA), aprogrammable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, processor 820 may be configured to operate a memory arrayusing a memory controller. In other cases, a memory controller may beintegrated into processor 820. Processor 820 may be configured toexecute computer-readable instructions stored in a memory to performvarious functions (e.g., functions or tasks supporting adapting to delayspread variation in wireless communication systems).

Memory 825 may include random access memory (RAM) and read only memory(ROM). The memory 825 may store computer-readable, computer-executablesoftware 830 including instructions that, when executed, cause theprocessor to perform various functions described herein. In some cases,the memory 825 may contain, among other things, a basic input/outputsystem (BIOS) which may control basic hardware and/or software operationsuch as the interaction with peripheral components or devices.

Software 830 may include code to implement aspects of the presentdisclosure, including code to support adapting to delay spread variationin wireless communication systems. Software 830 may be stored in anon-transitory computer-readable medium such as system memory or othermemory. In some cases, the software 830 may not be directly executableby the processor but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

Transceiver 835 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 835 may represent a wireless transceiver and may communicatebi-directionally with another wireless transceiver. The transceiver 835may also include a modem to modulate the packets and provide themodulated packets to the antennas for transmission, and to demodulatepackets received from the antennas.

In some cases, the wireless device may include a single antenna 840.However, in some cases the device may have more than one antenna 840,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

I/O controller 845 may manage input and output signals for device 805.I/O controller 845 may also manage peripherals not integrated intodevice 805. In some cases, I/O controller 845 may represent a physicalconnection or port to an external peripheral. In some cases, I/Ocontroller 845 may utilize an operating system such as iOS®, ANDROID®,MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operatingsystem.

FIG. 9 shows a block diagram 900 of a device 905 that supports adaptingto delay spread variation in wireless communication systems inaccordance with various aspects of the present disclosure. Device 905may be an example of aspects of a base station 105 as described withreference to FIG. 1. Device 905 may include receiver 910, base stationdelay spread manager 915, and transmitter 920. Device 905 may alsoinclude a processor. Each of these components may be in communicationwith one another (e.g., via one or more buses). In some examples,wireless communication systems may be or include a mmW system.

Receiver 910 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to adapting todelay spread variation in wireless communication systems, etc.).Information may be passed on to other components of the device. Thereceiver 910 may be an example of aspects of the transceiver 1235described with reference to FIG. 12. For example, receiver 910 mayreceive an uplink message from a UE 115 based on the updated referencesignal pattern or symbol prefix configuration. In some cases, the uplinkmessage includes a SRS or a beamforming measurement reference signal(MRS).

Base station delay spread manager 915 may be an example of aspects ofthe base station delay spread manager 1215 described with reference toFIG. 12. Base station delay spread manager 915 may receive an indicationof one or more propagation channel measurement parameters from the UE115, the one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter, update a reference signal pattern or asymbol prefix configuration based on the indication of the one or morepropagation channel measurement parameters, and transmit a configurationmessage to the UE 115 in response to receiving the indication of the oneor more propagation channel measurement parameters, the configurationmessage including an indication of the updated reference signal patternor symbol prefix configuration.

Base station delay spread manager 915 may also identify one or morepropagation channel measurement parameters including a delay spreadparameter, a multipath fading parameter, or a frequency selectivityparameter, update a reference signal pattern or a symbol prefixconfiguration based on the one or more propagation channel measurementparameters, and transmit a reference signal request to a UE 115 based onone or more propagation channel measurement parameters, the one or morepropagation channel measurement parameters including a delay spreadparameter, a multipath fading parameter, or a frequency selectivityparameter.

Transmitter 920 may transmit signals generated by other components ofthe device. In some examples, the transmitter 920 may be collocated witha receiver 910 in a transceiver module. For example, the transmitter 920may be an example of aspects of the transceiver 1235 described withreference to FIG. 12. The transmitter 920 may include a single antenna,or it may include a set of antennas. For example, transmitter 920 maytransmit a data communication to the UE 115 based on the updatedreference signal pattern or symbol prefix configuration.

FIG. 10 shows a block diagram 1000 of a device 1005 that supportsadapting to delay spread variation in wireless communication systems inaccordance with various aspects of the present disclosure. Device 1005may be an example of aspects of a device 905 or a base station 105 asdescribed with reference to FIGS. 1 and 9. Device 1005 may includereceiver 1010, base station delay spread manager 1015, and transmitter1020. Device 1005 may also include a processor. Each of these componentsmay be in communication with one another (e.g., via one or more buses).In some examples, wireless communication systems may be or include a mmWsystem.

Receiver 1010 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to adapting todelay spread variation in wireless communication systems, etc.).Information may be passed on to other components of the device. Thereceiver 1010 may be an example of aspects of the transceiver 1235described with reference to FIG. 12.

Base station delay spread manager 1015 may be an example of aspects ofthe base station delay spread manager 1215 described with reference toFIG. 12. Base station delay spread manager 1015 may also include channelmeasurement component 1025, dynamic configuration component 1030, andreference signal request component 1035.

Channel measurement component 1025 may receive an indication of one ormore propagation channel measurement parameters from a UE 115 (i.e.,downlink parameters), the one or more propagation channel measurementparameters including a delay spread parameter, a multipath fadingparameter, or a frequency selectivity parameter, transmit a request forthe UE 115 to transmit the indication of the one or more propagationchannel measurement parameters, where the indication is received basedon the request, and identify one or more propagation channel measurementparameters (i.e., uplink parameters) including a delay spread parameter,a multipath fading parameter, or a frequency selectivity parameter.

Dynamic configuration component 1030 may update a reference signalpattern or a symbol prefix configuration based on the indication of theone or more propagation channel measurement parameters, transmit aconfiguration message to the UE 115 in response to receiving theindication of the one or more propagation channel measurementparameters, the configuration message including an indication of theupdated reference signal pattern or symbol prefix configuration,identify a CoMP configuration, a SIMO configuration, a MIMOconfiguration or additional downlink control information, where thereference signal pattern or the symbol prefix configuration is updatedbased on the CoMP configuration, the SIMO configuration, the MIMOconfiguration, or the additional downlink control information, andupdate a reference signal pattern or a symbol prefix configuration basedon the configuration message.

In some cases, the configuration message includes a PDCCH message. Insome cases, the PDCCH message includes a common PDCCH message. In somecases, the PDCCH message includes an enhanced frequency or receive powerPDCCH message. In some cases, the one or more propagation channelmeasurement parameters are based on a channel reciprocity of a TDDconfiguration.

Reference signal request component 1035 may transmit a reference signalrequest to a UE 115 based on one or more propagation channel measurementparameters, the one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter.

Transmitter 1020 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1020 may be collocatedwith a receiver 1010 in a transceiver module. For example, thetransmitter 1020 may be an example of aspects of the transceiver 1235described with reference to FIG. 12. The transmitter 1020 may include asingle antenna, or it may include a set of antennas.

FIG. 11 shows a block diagram 1100 of a base station delay spreadmanager 1115 that supports adapting to delay spread variation inwireless communication systems in accordance with various aspects of thepresent disclosure. The base station delay spread manager 1115 may be anexample of aspects of a base station delay spread manager 1215 describedwith reference to FIGS. 9, 10, and 12. The base station delay spreadmanager 1115 may include channel measurement component 1120, dynamicconfiguration component 1125, reference signal request component 1130,reference signal component 1135, semi-static configuration component1140, and beamforming component 1145. Each of these modules maycommunicate, directly or indirectly, with one another (e.g., via one ormore buses). In some examples, wireless communication systems may be orinclude a mmW system.

Channel measurement component 1120 may receive an indication of one ormore propagation channel measurement parameters from a UE 115, the oneor more propagation channel measurement parameters including a delayspread parameter, a multipath fading parameter, or a frequencyselectivity parameter, transmit a request for the UE 115 to transmit theindication of the one or more propagation channel measurementparameters, where the indication is received based on the request, andidentify one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter.

Dynamic configuration component 1125 may update a reference signalpattern or a symbol prefix configuration based on the indication of theone or more propagation channel measurement parameters, transmit aconfiguration message to the UE 115 in response to receiving theindication of the one or more propagation channel measurementparameters, the configuration message including an indication of theupdated reference signal pattern or symbol prefix configuration,identify a CoMP configuration, a SIMO configuration, a MIMOconfiguration or additional downlink control information.

Reference signal request component 1130 may transmit a reference signalrequest to a UE 115 based on one or more propagation channel measurementparameters, the one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter. Reference signal component 1135 maytransmit one or more reference signals based on the updated referencesignal pattern.

Semi-static configuration component 1140 may transmit a broadcast systeminformation message or a RRC message, where the reference signal patternor the symbol prefix configuration is updated based on the broadcastsystem information message or the RRC message. Beamforming component1145 may transmit an additional configuration message using a differentbeamforming direction, where the additional configuration messageincludes an indication of the updated reference signal pattern or symbolprefix configuration.

FIG. 12 shows a diagram of a system 1200 including a device 1205 thatsupports adapting to delay spread variation in wireless communicationsystems in accordance with various aspects of the present disclosure.Device 1205 may be an example of or include the components of a basestation 105 as described above, e.g., with reference to FIG. 1. Device1205 may include components for bi-directional voice and datacommunications including components for transmitting and receivingcommunications, including base station delay spread manager 1215,processor 1220, memory 1225, software 1230, transceiver 1235, antenna1240, network communications manager 1245, and base stationcommunications manager 1250. These components may be in electroniccommunication via one or more busses (e.g., bus 1210). Device 1205 maycommunicate wirelessly with one or more UEs 115. In some examples,wireless communication systems may be or include a mmW system.

Processor 1220 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, processor 1220 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into processor 1220. Processor 1220 may be configured toexecute computer-readable instructions stored in a memory to performvarious functions (e.g., functions or tasks supporting adapting to delayspread variation in wireless communication systems).

Memory 1225 may include RAM and ROM. The memory 1225 may storecomputer-readable, computer-executable software 1230 includinginstructions that, when executed, cause the processor to perform variousfunctions described herein. In some cases, the memory 1225 may contain,among other things, a BIOS which may control basic hardware and/orsoftware operation such as the interaction with peripheral components ordevices.

Software 1230 may include code to implement aspects of the presentdisclosure, including code to support adapting to delay spread variationin wireless communication systems. Software 1230 may be stored in anon-transitory computer-readable medium such as system memory or othermemory. In some cases, the software 1230 may not be directly executableby the processor but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

Transceiver 1235 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1235 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1235 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1240.However, in some cases the device may have more than one antenna 1240,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

Network communications manager 1245 may manage communications with thecore network (e.g., via one or more wired backhaul links). For example,the network communications manager 1245 may manage the transfer of datacommunications for client devices, such as one or more UEs 115.

Base station communications manager 1250 may manage communications withother base stations 105, and may include a controller or scheduler forcontrolling communications with UEs 115 in cooperation with other basestations 105. For example, the base station communications manager 1250may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, base station communications manager 1250may provide an X2 interface within an LTE/LTE-A wireless communicationnetwork technology to provide communication between base stations 105.

FIG. 13 shows a flowchart illustrating a method 1300 for adapting todelay spread variation in wireless communication systems in accordancewith various aspects of the present disclosure. The operations of method1300 may be implemented by a UE 115 or its components as describedherein. For example, the operations of method 1300 may be performed by aUE delay spread manager as described with reference to FIGS. 5 through8. In some examples, a UE 115 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware. In someexamples, wireless communication systems may be or include a mmW system.

At block 1305 the UE 115 may identify one or more propagation channelmeasurement parameters including a delay spread parameter, a multipathfading parameter, or a frequency selectivity parameter. The operationsof block 1305 may be performed according to the methods described withreference to FIGS. 1 through 4. In certain examples, aspects of theoperations of block 1305 may be performed by a channel measurementcomponent as described with reference to FIGS. 5 through 8.

At block 1310 the UE 115 may transmit an indication of the one or morepropagation channel measurement parameters to a base station 105. Theoperations of block 1310 may be performed according to the methodsdescribed with reference to FIGS. 1 through 4. In certain examples,aspects of the operations of block 1310 may be performed by a channelmeasurement indication component as described with reference to FIGS. 5through 8.

At block 1315 the UE 115 may receive a configuration message from thebase station 105 in response to transmitting the indication of the oneor more propagation channel measurement parameters. The operations ofblock 1315 may be performed according to the methods described withreference to FIGS. 1 through 4. In certain examples, aspects of theoperations of block 1315 may be performed by a dynamic configurationcomponent as described with reference to FIGS. 5 through 8.

At block 1320 the UE 115 may update a reference signal pattern or asymbol prefix configuration based on the configuration message. Theoperations of block 1320 may be performed according to the methodsdescribed with reference to FIGS. 1 through 4. In certain examples,aspects of the operations of block 1320 may be performed by a dynamicconfiguration component as described with reference to FIGS. 5 through8.

FIG. 14 shows a flowchart illustrating a method 1400 for adapting todelay spread variation in wireless communication systems in accordancewith various aspects of the present disclosure. The operations of method1400 may be implemented by a UE 115 or its components as describedherein. For example, the operations of method 1400 may be performed by aUE delay spread manager as described with reference to FIGS. 5 through8. In some examples, a UE 115 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware. In someexamples, wireless communication systems may be or include a mmW system.

At block 1405 the UE 115 may identify one or more propagation channelmeasurement parameters including a delay spread parameter, a multipathfading parameter, or a frequency selectivity parameter. The operationsof block 1405 may be performed according to the methods described withreference to FIGS. 1 through 4. In certain examples, aspects of theoperations of block 1405 may be performed by a channel measurementcomponent as described with reference to FIGS. 5 through 8.

At block 1410 the UE 115 may transmit an indication of the one or morepropagation channel measurement parameters to a base station 105. Theoperations of block 1410 may be performed according to the methodsdescribed with reference to FIGS. 1 through 4. In certain examples,aspects of the operations of block 1410 may be performed by a channelmeasurement indication component as described with reference to FIGS. 5through 8.

At block 1415 the UE 115 may receive a configuration message from thebase station 105 in response to transmitting the indication of the oneor more propagation channel measurement parameters. The operations ofblock 1415 may be performed according to the methods described withreference to FIGS. 1 through 4. In certain examples, aspects of theoperations of block 1415 may be performed by a dynamic configurationcomponent as described with reference to FIGS. 5 through 8.

At block 1420 the UE 115 may update a reference signal pattern or asymbol prefix configuration based on the configuration message. Theoperations of block 1420 may be performed according to the methodsdescribed with reference to FIGS. 1 through 4. In certain examples,aspects of the operations of block 1420 may be performed by a dynamicconfiguration component as described with reference to FIGS. 5 through8.

At block 1425 the UE 115 may receive one or more reference signals basedon the updated reference signal pattern. The operations of block 1425may be performed according to the methods described with reference toFIGS. 1 through 4. In certain examples, aspects of the operations ofblock 1425 may be performed by a reference signal component as describedwith reference to FIGS. 5 through 8.

FIG. 15 shows a flowchart illustrating a method 1500 for adapting todelay spread variation in wireless communication systems in accordancewith various aspects of the present disclosure. The operations of method1500 may be implemented by a UE 115 or its components as describedherein. For example, the operations of method 1500 may be performed by aUE delay spread manager as described with reference to FIGS. 5 through8. In some examples, a UE 115 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware. In someexamples, wireless communication systems may be or include a mmW system.

At block 1505 the UE 115 may identify one or more propagation channelmeasurement parameters including a delay spread parameter, a multipathfading parameter, or a frequency selectivity parameter. The operationsof block 1505 may be performed according to the methods described withreference to FIGS. 1 through 4. In certain examples, aspects of theoperations of block 1505 may be performed by a channel measurementcomponent as described with reference to FIGS. 5 through 8.

At block 1510 the UE 115 may transmit an indication of the one or morepropagation channel measurement parameters to a base station 105. Theoperations of block 1510 may be performed according to the methodsdescribed with reference to FIGS. 1 through 4. In certain examples,aspects of the operations of block 1510 may be performed by a channelmeasurement indication component as described with reference to FIGS. 5through 8.

At block 1515 the UE 115 may receive a configuration message from thebase station 105 in response to transmitting the indication of the oneor more propagation channel measurement parameters. The operations ofblock 1515 may be performed according to the methods described withreference to FIGS. 1 through 4. In certain examples, aspects of theoperations of block 1515 may be performed by a dynamic configurationcomponent as described with reference to FIGS. 5 through 8.

At block 1520 the UE 115 may update a reference signal pattern or asymbol prefix configuration based on the configuration message. Theoperations of block 1520 may be performed according to the methodsdescribed with reference to FIGS. 1 through 4. In certain examples,aspects of the operations of block 1520 may be performed by a dynamicconfiguration component as described with reference to FIGS. 5 through8.

At block 1525 the UE 115 may receive a data communication from the basestation 105 based on the updated reference signal pattern or symbolprefix configuration. The operations of block 1525 may be performedaccording to the methods described with reference to FIGS. 1 through 4.In certain examples, aspects of the operations of block 1525 may beperformed by a receiver as described with reference to FIGS. 5 through8.

FIG. 16 shows a flowchart illustrating a method 1600 for adapting todelay spread variation in wireless communication systems in accordancewith various aspects of the present disclosure. The operations of method1600 may be implemented by a base station 105 or its components asdescribed herein. For example, the operations of method 1600 may beperformed by a base station delay spread manager as described withreference to FIGS. 9 through 12. In some examples, a base station 105may execute a set of codes to control the functional elements of thedevice to perform the functions described below. In some examples,wireless communication systems may be or include a mmW system.Additionally or alternatively, the base station 105 may perform aspectsthe functions described below using special-purpose hardware.

At block 1605 the base station 105 may receive an indication of one ormore propagation channel measurement parameters from a UE 115, the oneor more propagation channel measurement parameters including a delayspread parameter, a multipath fading parameter, or a frequencyselectivity parameter. The operations of block 1605 may be performedaccording to the methods described with reference to FIGS. 1 through 4.In certain examples, aspects of the operations of block 1605 may beperformed by a channel measurement component as described with referenceto FIGS. 9 through 12.

At block 1610 the base station 105 may update a reference signal patternor a symbol prefix configuration based on the indication of the one ormore propagation channel measurement parameters. The operations of block1610 may be performed according to the methods described with referenceto FIGS. 1 through 4. In certain examples, aspects of the operations ofblock 1610 may be performed by a dynamic configuration component asdescribed with reference to FIGS. 9 through 12.

At block 1615 the base station 105 may transmit a configuration messageto the UE 115 in response to receiving the indication of the one or morepropagation channel measurement parameters, the configuration messageincluding an indication of the updated reference signal pattern orsymbol prefix configuration. The operations of block 1615 may beperformed according to the methods described with reference to FIGS. 1through 4. In certain examples, aspects of the operations of block 1615may be performed by a dynamic configuration component as described withreference to FIGS. 9 through 12.

FIG. 17 shows a flowchart illustrating a method 1700 for adapting todelay spread variation in wireless communication systems in accordancewith various aspects of the present disclosure. The operations of method1700 may be implemented by a UE 115 or its components as describedherein. For example, the operations of method 1700 may be performed by aUE delay spread manager as described with reference to FIGS. 5 through8. In some examples, a UE 115 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware. In someexamples, wireless communication systems may be or include a mmW system.

At block 1705 the UE 115 may receive a reference signal request from abase station 105 based on one or more propagation channel measurementparameters, the one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter. The operations of block 1705 may beperformed according to the methods described with reference to FIGS. 1through 4. In certain examples, aspects of the operations of block 1705may be performed by a dynamic configuration component as described withreference to FIGS. 5 through 8.

At block 1710 the UE 115 may update a reference signal pattern based onthe reference signal request. The operations of block 1710 may beperformed according to the methods described with reference to FIGS. 1through 4. In certain examples, aspects of the operations of block 1710may be performed by a dynamic configuration component as described withreference to FIGS. 5 through 8.

At block 1715 the UE 115 may transmit an uplink message to the basestation 105 based on the updated reference signal pattern. Theoperations of block 1715 may be performed according to the methodsdescribed with reference to FIGS. 1 through 4. In certain examples,aspects of the operations of block 1715 may be performed by atransmitter as described with reference to FIGS. 5 through 8.

FIG. 18 shows a flowchart illustrating a method 1800 for adapting todelay spread variation in wireless communication systems in accordancewith various aspects of the present disclosure. The operations of method1800 may be implemented by a base station 105 or its components asdescribed herein. For example, the operations of method 1800 may beperformed by a base station delay spread manager as described withreference to FIGS. 9 through 12. In some examples, a base station 105may execute a set of codes to control the functional elements of thedevice to perform the functions described below. Additionally oralternatively, the base station 105 may perform aspects the functionsdescribed below using special-purpose hardware. In some examples,wireless communication systems may be or include a mmW system.

At block 1805 the base station 105 may identify one or more propagationchannel measurement parameters including a delay spread parameter, amultipath fading parameter, or a frequency selectivity parameter. Theoperations of block 1805 may be performed according to the methodsdescribed with reference to FIGS. 1 through 4. In certain examples,aspects of the operations of block 1805 may be performed by a channelmeasurement component as described with reference to FIGS. 9 through 12.

At block 1810 the base station 105 may update a reference signal patternor a symbol prefix configuration based on the configuration message. Theoperations of block 1810 may be performed according to the methodsdescribed with reference to FIGS. 1 through 4. In certain examples,aspects of the operations of block 1810 may be performed by a dynamicconfiguration component as described with reference to FIGS. 9 through12.

At block 1815 the base station 105 may transmit a reference signalrequest to a UE 115 based on one or more propagation channel measurementparameters, the one or more propagation channel measurement parametersincluding a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter. The operations of block 1815 may beperformed according to the methods described with reference to FIGS. 1through 4. In certain examples, aspects of the operations of block 1815may be performed by a reference signal request component as describedwith reference to FIGS. 9 through 12.

At block 1820 the base station 105 may receive an uplink message fromthe UE 115 based on the updated reference signal pattern or symbolprefix configuration. The operations of block 1820 may be performedaccording to the methods described with reference to FIGS. 1 through 4.In certain examples, aspects of the operations of block 1820 may beperformed by a receiver as described with reference to FIGS. 9 through12.

It should be noted that the methods described above describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Furthermore, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.The terms “system” and “network” are often used interchangeably. A codedivision multiple access (CDMA) system may implement a radio technologysuch as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc.CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releasesmay be commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. Atime division multiple access (TDMA) system may implement a radiotechnology such as Global System for Mobile Communications (GSM).

An orthogonal frequency division multiple access (OFDMA) system mayimplement a radio technology such as Ultra Mobile Broadband (UMB),Evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM,etc. UTRA and E-UTRA are part of Universal Mobile Telecommunicationssystem (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A)are releases of Universal Mobile Telecommunications System (UMTS) thatuse E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and Global System for Mobilecommunications (GSM) are described in documents from the organizationnamed “3rd Generation Partnership Project” (3GPP). CDMA2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). The techniques described herein may beused for the systems and radio technologies mentioned above as well asother systems and radio technologies. While aspects an LTE system may bedescribed for purposes of example, and LTE terminology may be used inmuch of the description, the techniques described herein are applicablebeyond LTE applications.

In LTE/LTE-A networks, including such networks described herein, theterm evolved node B (eNB) may be generally used to describe the basestations. The wireless communications system or systems described hereinmay include a heterogeneous LTE/LTE-A network in which different typesof evolved node B (eNBs) provide coverage for various geographicalregions. For example, each eNB or base station may provide communicationcoverage for a macro cell, a small cell, or other types of cell. Theterm “cell” may be used to describe a base station, a carrier orcomponent carrier associated with a base station, or a coverage area(e.g., sector, etc.) of a carrier or base station, depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an accesspoint, a radio transceiver, a NodeB, eNodeB (eNB), Home NodeB, a HomeeNodeB, or some other suitable terminology. The geographic coverage areafor a base station may be divided into sectors making up a portion ofthe coverage area. The wireless communications system or systemsdescribed herein may include base stations of different types (e.g.,macro or small cell base stations). The UEs described herein may be ableto communicate with various types of base stations and network equipmentincluding macro eNBs, small cell eNBs, relay base stations, and thelike. There may be overlapping geographic coverage areas for differenttechnologies.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell is alower-powered base station, as compared with a macro cell, that mayoperate in the same or different (e.g., licensed, unlicensed, etc.)frequency bands as macro cells. Small cells may include pico cells,femto cells, and micro cells according to various examples. A pico cell,for example, may cover a small geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell may also cover a small geographic area (e.g., ahome) and may provide restricted access by UEs having an associationwith the femto cell (e.g., UEs in a closed subscriber group (CSG), UEsfor users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., component carriers). A UE may be able to communicate with varioustypes of base stations and network equipment including macro eNBs, smallcell eNBs, relay base stations, and the like.

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The downlink transmissions described herein may also be called forwardlink transmissions while the uplink transmissions may also be calledreverse link transmissions. Each communication link describedherein—including, for example, wireless communications system 100 and200 of FIGS. 1 and 2—may include one or more carriers, where eachcarrier may be a signal made up of multiple sub-carriers (e.g., waveformsignals of different frequencies).

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope and spirit of the disclosure and appended claims. For example,due to the nature of software, functions described above can beimplemented using software executed by a processor, hardware, firmware,hardwiring, or combinations of any of these. Features implementingfunctions may be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations. As used herein, including in the claims,the term “and/or,” when used in a list of two or more items, means thatany one of the listed items can be employed by itself, or anycombination of two or more of the listed items can be employed. Forexample, if a composition is described as containing components A, B,and/or C, the composition can contain A alone; B alone; C alone; A and Bin combination; A and C in combination; B and C in combination; or A, B,and C in combination. Also, as used herein, including in the claims,“or” as used in a list of items (for example, a list of items prefacedby a phrase such as “at least one of” or “one or more of”) indicates aninclusive list such that, for example, a phrase referring to “at leastone of” a list of items refers to any combination of those items,including single members. As an example, “at least one of: A, B, or C”is intended to cover A, B, C, A-B, A-C, B-C, and A-B-C., as well as anycombination with multiples of the same element (e.g., A-A A-A-A, A-A-B,A-A-C, A-B-B, A-C-C, B-B, B-B-B, B-B-C, C-C, and C-C-C or any otherordering of A, B, and C).

As used herein, the phrase “based on” shall not be construed as areference to a closed set of conditions. For example, an exemplaryfeature that is described as “based on condition A” may be based on botha condition A and a condition B without departing from the scope of thepresent disclosure. In other words, as used herein, the phrase “basedon” shall be construed in the same manner as the phrase “based at leastin part on.”

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media maycomprise RAM, ROM, electrically erasable programmable read only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave are included in the definition of medium. Disk and disc,as used herein, include CD, laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communication, comprising:identifying one or more propagation channel measurement parameterscomprising a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter; transmitting an indication of the oneor more propagation channel measurement parameters to a base station;receiving a configuration message from the base station in response totransmitting the indication of the one or more propagation channelmeasurement parameters; and updating a reference signal pattern or asymbol prefix configuration based at least in part on the configurationmessage.
 2. The method of claim 1, further comprising: receiving one ormore reference signals based at least in part on the updated referencesignal pattern.
 3. The method of claim 2, wherein the reference signalpattern comprises a pattern for a channel state information referencesignal (CSI-RS), a cell specific reference signal (CRS), a demodulationreference signal (DMRS), a beamforming reference signal (BRS), abeamforming measurement reference signal (MRS), or a sounding referencesignal (SRS).
 4. The method of claim 1, further comprising: receiving adata communication from the base station based at least in part on theupdated reference signal pattern or symbol prefix configuration.
 5. Themethod of claim 1, wherein the symbol prefix configuration comprises anorthogonal frequency division multiplexing (OFDM) cyclic prefixconfiguration, a single carrier frequency division multiplexing (SC-FDM)cyclic prefix configuration, or an SC-FDM guard interval configuration.6. The method of claim 5, wherein the SC-FDM guard intervalconfiguration comprises an indication of a number of zeroes to beappended or prepended to a data symbol prior to a discrete Fouriertransform spreading.
 7. The method of claim 1, further comprising:receiving a broadcast system information message or a radio resourcecontrol (RRC) message, wherein the reference signal pattern or thesymbol prefix configuration are updated based at least in part on thebroadcast system information message or the RRC message.
 8. The methodof claim 1, wherein the configuration message comprises a physicaldownlink control (PDCCH) message.
 9. The method of claim 8, wherein thePDCCH message comprises a common PDCCH message.
 10. The method of claim9, wherein the PDCCH message comprises an enhanced frequency or transmitpower PDCCH message.
 11. The method of claim 1, further comprising:identifying a coordinated multipoint (CoMP) configuration, asingle-input multiple-output (SIMO) configuration, a multiple-inputmultiple-output (MIMO) configuration or additional downlink controlinformation, wherein the reference signal pattern or the symbol prefixconfiguration is updated based on the CoMP configuration, the SIMOconfiguration, the MIMO configuration, or the additional downlinkcontrol information.
 12. The method of claim 1, wherein the indicationis transmitted based at least in part on a periodic reportingconfiguration.
 13. The method of claim 1, further comprising: receivinga request to transmit the indication of the one or more propagationchannel measurement parameters from the base station, wherein theindication is transmitted based at least in part on the request.
 14. Themethod of claim 1, wherein the symbol prefix configuration comprises aplurality of cyclic prefix durations associated with a plurality ofsymbol periods of a subframe, or a plurality of symbol periods of aslot, or a combination thereof.
 15. The method of claim 1, wherein theconfiguration message comprises a mapping between a subframe number anda cyclic prefix duration, or a mapping between a slot number and thecyclic prefix duration, and wherein the symbol prefix configuration isupdated based at least in part on the mapping and the subframe number orthe mapping and the slot number.
 16. The method of claim 1, wherein theconfiguration message comprises a combined indication of the referencesignal pattern and the symbol prefix configuration.
 17. A method forwireless communication, comprising: receiving an indication of one ormore propagation channel measurement parameters from a user equipment(UE), the one or more propagation channel measurement parameterscomprising a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter; updating a reference signal pattern ora symbol prefix configuration based at least in part on the indicationof the one or more propagation channel measurement parameters; andtransmitting a configuration message to the UE in response to receivingthe indication of the one or more propagation channel measurementparameters, the configuration message comprising an indication of theupdated reference signal pattern or symbol prefix configuration.
 18. Themethod of claim 17, further comprising: transmitting one or morereference signals based at least in part on the updated reference signalpattern.
 19. The method of claim 17, further comprising: transmitting adata communication to the UE based at least in part on the updatedreference signal pattern or symbol prefix configuration.
 20. The methodof claim 17, further comprising: transmitting a broadcast systeminformation message or a radio resource control (RRC) message, whereinthe reference signal pattern or the symbol prefix configuration isupdated based at least in part on the broadcast system informationmessage or the RRC message.
 21. The method of claim 17, wherein theconfiguration message comprises a physical downlink control (PDCCH)message.
 22. The method of claim 21, wherein the PDCCH message comprisesa common PDCCH message.
 23. The method of claim 22, wherein the PDCCHmessage comprises an enhanced frequency or receive power PDCCH message.24. The method of claim 17, further comprising: identifying acoordinated multipoint (CoMP) configuration, a single-inputmultiple-output (SIMO) configuration, a multiple-input multiple-output(MIMO) configuration or additional downlink control information, whereinthe reference signal pattern or the symbol prefix configuration isupdated based on the CoMP configuration, the SIMO configuration, theMIMO configuration, or the additional downlink control information. 25.The method of claim 17, further comprising: transmitting a request forthe UE to transmit the indication of the one or more propagation channelmeasurement parameters, wherein the indication is received based atleast in part on the request.
 26. A method for wireless communication,comprising: receiving a reference signal request from a base stationbased at least in part on one or more propagation channel measurementparameters, the one or more propagation channel measurement parameterscomprising a delay spread parameter, a multipath fading parameter, or afrequency selectivity parameter; updating a reference signal patternbased at least in part on the reference signal request; and transmittingan uplink message to the base station based at least in part on theupdated reference signal pattern.
 27. The method of claim 26, whereinthe uplink message comprises a sounding reference signal (SRS) or abeamforming measurement reference signal (MRS).
 28. A method forwireless communication, comprising: identifying one or more propagationchannel measurement parameters comprising a delay spread parameter, amultipath fading parameter, or a frequency selectivity parameter;updating a reference signal pattern or a symbol prefix configurationbased at least in part on the one or more propagation channelmeasurement parameters; transmitting a reference signal request to auser equipment (UE), wherein the reference signal request indicates theupdated reference signal pattern or symbol prefix configuration; andreceiving an uplink message from the UE in response to the referencesignal request, wherein the uplink message is based at least in part onthe reference signal pattern or the symbol prefix configuration.
 29. Themethod of claim 28, wherein the uplink message comprises a soundingreference signal (SRS) or a beamforming measurement reference signal(MRS).
 30. The method of claim 28, wherein the one or more propagationchannel measurement parameters are based at least in part on a channelreciprocity of a time division duplexing (TDD) configuration.